The present invention relates generally to air dryers, and more specifically, to an air dryer with an integral pre-filter for a brake system for vehicles.
Air dryers employing membranes consisting of a permeable membrane capable of blocking the passage of nitrogen and oxygen molecules, but allowing water vapor molecules to pass through, as described in U.S. Pat. Nos. 6,719,825 and 5,525,143 amongst many others. In one variation of the technology, the air to be dried passes through the center of the membrane element. The membrane permits the passage of the water vapor to the outside of the membrane, but prevents the passage of the air to the outside of the membrane, thereby drying the air.
To work effectively, the outside of the membrane must be kept dry and at a lower pressure than the inside, creating the partial pressure differential to drive the water vapor out. This is done by providing some fraction of the dry output air as a counter flow sweep air across the outside of the membrane. The sweep air can be provided by sweep air orifice(s) connecting the dry air in the membrane air dryer outlet to the sweep air chamber surrounding the outside of the membrane. The orifices control the volume of sweep air, typically 10-20% of the dryer capacity and create a pressure drop in the sweep air volume. The sweep air and entrapped moisture are expelled to atmosphere.
U.S. Pat. No. 6,719,825 shows a control valve at the inlet for the sweep air. U.S. Pat. No. 5,375,620 shows a self-adjusting flow metering device for the sweep air. An air dryer including a coalescing and charcoal pre-filters and a membrane filter is also shown by U.S. Pat. No. 6,719,825.
The present disclosure is directed to an air dryer, for example, for locomotives, packaged to fit inside a reservoir with a pre-filter exterior the reservoir. The air dryer is generally cylindrical with a circular mounting flange on one end, which bolts to a similar mounting flange welded to the end of the reservoir. This arrangement solves the problem of finding room for the air dryer between main reservoir #1 and #2 on a locomotive, protects the air dryer and especially the vulnerable membrane element from the very high ambient temperatures (as high as 300° F.) during operation of the locomotive in tunnels; protects the air dryer from environmental hazards, like flying stone ballast; eliminates installation piping, and minimizes weight.
A pre-filter includes a housing having an air inlet, an air outlet, a first chamber and a second chamber concentric to and interior the first chamber. A coalescer is in the first chamber and a first filter is in the second chamber. A first inlet of the first chamber is interior the coalescer and connected to the air inlet and a first outlet of the first chamber being exterior the coalescer. A second inlet of the second chamber is interior the first filter and connected to the first outlet of the first chamber and a second outlet of the second chamber is exterior the first filter and connected to the air outlet.
The first filter may be a charcoal filter. A second filter is in the first chamber concentric to the coalescer between the first inlet and the first outlet.
The first inlet may be a plurality of first inlets; and the housing includes a third chamber connecting the air inlet to the first inlets. The third chamber is an annulus and the air input is on an outer circumference of the annulus. The first outlet may be a plurality of first outlets and the second inlet may be a plurality of second inlets; and the housing includes a fourth chamber connecting the first outlets to the second inlets. The second outlet may be a plurality of second outlets; and the housing includes a fifth chamber connecting the second outlets to the air output.
The filter includes a membrane separator in the housing connecting the second outlet of the second chamber and the air outlet. A first drain on the housing is connected to the first chamber and a second drain on the housing is connected to a sweep air outlet of the membrane separator. A valve is connected between the sweep air outlet of the membrane separator and the second drain for controlling the draining of the liquid and sweep air flow through the membrane separator. Alternatively, the valve is connected to a sweep air inlet of the membrane separator for controlling sweep air flow through the membrane separator. A drain may also be provided for the annular third chamber.
The housing includes a first and second portions removably secured to each other. The first and second chambers are in the second portion of the housing and the first filter is mounted to and removable with the first portion of the housing as a unit. The housing includes a third portion removably secured to the second portion of the housing; and a membrane separator is in the third portion of the housing connecting the second outlet of the second chamber and the air output.
Another filter includes a housing having first and second portions separated by a center portion and the housing portions are removably secured to each other. An air inlet of the filter is on the center portion and an air outlet of the filter is on an end face of the second portion. A first chamber and a second chamber concentric to and interior the first chamber are provided and a coalescer is in the first chamber. A first inlet of the first chamber is interior the coalescer and connected to the air inlet via a first passage in the center portion and a first outlet of the first chamber is exterior the coalescer and connected to the second chamber. A third chamber is in the second housing portion and a membrane separator is in the third chamber and has an outlet connected to the air outlet and having an inlet. A second passage in the center portion connects the second chamber to the inlet of the membrane filter.
The filter includes an annulus shaped fourth chamber in the center portion connecting the air inlet to the first inlet and the air input is on an outer circumference of the annulus. A drain is connected to the first chamber and a drain is connected to the fourth chamber. Another drain is connected to a sweep air outlet of the membrane separator.
The filter may be mounted in a reservoir having an inlet. The filter extends from a reservoir inlet into the interior of the reservoir so that the housing's air inlet is the inlet of the reservoir, the housing's air outlet is interior the reservoir.
These and other aspects of the present method will become apparent from the following detailed description of the method, when considered in conjunction with accompanying drawings.